1. Field of the Invention
The present invention relates to a clock generation circuit. In particular, the present invention relates to a clock generation circuit which generates a clock signal having the given number of waves in a certain period. The present invention also relates to a semiconductor device including the clock generation circuit.
2. Description of the Related Art
In recent years, semiconductor devices which are capable of transmitting and receiving a signal wirelessly, such as an RFID (Radio Frequency Identification) tag (also referred to as an ID tag, an IC tag, an IC chip, an RF tag, a wireless tag, a wireless chip, or an electronic tag) have been studied and started to be introduced on a trial basis to corporations, markets, and the like (see Patent Document 1: Japanese Published Patent Application No. 2006-196001).
Such a semiconductor device operates based on a signal which is received from a reader/writer. Specifically, a signal outputted from a transmitting circuit provided in the reader/writer is inputted to a receiving circuit provided in the semiconductor device such as an RFID tag.
In general, in the case where signals are transmitted or received between a transmitting circuit provided in a reader/writer or the like which is externally located and a receiving circuit provided in an RFID tag or the like, the signals are transmitted and received using clock signals which differ from circuit to circuit.